Turbocharger with progressively variable a/r ratio

ABSTRACT

An improvement to a turbocharger having a housing ( 10 ) with a slot ( 25 ) located along a mid-line of the housing ( 10 ) above the turbine wheel ( 29 )  10  and a tongue ( 15 ) defining the end of an initial inlet throat area ( 11 ) of the housing ( 10 ), the slot ( 25 ) permitting inlet exhaust gas which flows past the tongue ( 15 ) to flow into the turbine wheel ( 29 ), the improvement being a pivoting vane ( 50 ) aligned with the slot ( 25 ) and having an upstream end ( 55 ) located at a downstream end ( 57 ) of the tongue ( 15 ). When the vane ( 50 ) is in its fully closed position ( 60 ), the inlet exhaust gas is prevented from flowing into the slot ( 25 ) and, therefore, the turbine wheel ( 29 ), until the inlet exhaust gas passes the downstream end ( 57 ) of the vane ( 50 ). The vane ( 50 ) effectively extends the tongue ( 15 ) to define a revised inlet throat area ( 12 ). The A/R ratio of the housing ( 10 ) progressively varies as the vane ( 50 ) pivots between the fully opened ( 70 ) and fully closed ( 60 ) positions.

BACKGROUND OF THE INVENTION

This invention relates generally to turbochargers for motor vehiclesand, more specifically, to means for progressively varying the A/R(Area/Radius) ratio of a turbocharger.

Turbochargers are well known devices used in all forms of vehicles forsupplying air to the intake of an internal combustion engine atpressures above atmospheric pressure (“boost pressures”). A conventionalturbocharger includes a turbine rotor or wheel with a plurality of finsor blades inside a volute turbine housing. The turbine rotor is rotatedby exhaust gases from the engine which impinge upon the turbine blades.The rotor, via a connecting shaft, provides the driving torque to acompressor. Ambient air fed to the compressor creates a boost pressurethat is fed to the intake manifold of the engine.

The flow capacity of the exhaust turbine is a function of the housingvolute areas and the passage of the exhaust gases as it strikes theturbine blades. The flow of exhaust gas has to be regulated to controlthe compressor speed to create the desired boost in manifold pressure. Atypical centrifugal compressor includes an impeller driven at high speedby the turbine rotor. A diffuser surrounding the impeller causes theambient air to increase in pressure which is directed to the intakemanifold.

One particular goal with any turbocharger is the need for a quickresponse, i.e., prevent “turbo lag,” a delay between the time when highpower output is first demanded of the engine by setting the throttle toa wide open position and the time when a boost in the inlet manifold airpressure is delivered by the compressor. In some instances turbo lagcould result in a dangerous driving situation when substantiallyinstantaneous response is desired. If the turbocharger is large enoughto provide the maximum horsepower for an internal combustion engine,then it will have excessive and potentially unsafe lag when the throttleis increased. If the turbocharger is reduced in size to minimize turbolag, then efficiency is lost at higher engine rpms.

Some early turbocharger designs sought to solve the problem of turbo lagwithin a certain range of low engine speeds, such as when the engine isidling, by adding a regulated air supply to increase the mass of airentering the turbocharger intake and being forced into the enginemanifold. At idle speed, the engine exhaust is insufficient to maintainthe speed and charging-air output of the compressor section of theturbocharger, causing the turbocharger to “lag behind” the engine inperformance. To maintain the speed of the turbocharger, a pair ofnozzles penetrates the housing in opposite directions and injects airgenerally tangentially to the outer tips of the rotor blades. The airpressure provided by the nozzles acts as a “jet assist” in theturbocharger compressor when the engine is at idling speed (see U.S.Pat. No. 3,190,068 to Williams et al., Turbocharger for CompressorDriving Engine, issued Jun. 22, 1965, and U.S. Pat. No. 3,363,412, toFischer et al., System for Maintaining Turbocharger Compressor Speed,issued Jan. 16, 1968). Another design positions nozzles at preselectedpoints about the turbine rotor and directs air through the nozzles toimpinge the blades and, in addition to providing a jet assist, preventresonant vibration conditions in the rotor for its entire rotationalspeed range (see U.S. Pat. No. 3,396,534 to Bernson et al., AirImpingement Nozzle Arrangement for a Turbocharger Compressor and anImproved Method of Employing Air Impingement, issued Aug. 13, 1968).

The air-assisted designs do not operate to minimize turbo lag when theturbocharger is already in a spun-up condition and the engine is atnormal operating speed but requires additional horsepower. Furthermore,the air-assisted designs require a waste gate to handle the totalexhaust flow at maximum horsepower.

Other designs have proposed variable volute turbines; variable geometryturbines; electrically driven turbines; moveable or pivoting vanes,gates and walls for guiding, dividing, or changing the direction theexhaust gases relative to the turbine rotor and thereby control itsrotational speed.

Variable volute turbines make use of a sliding or flexible dividing wallto change the geometry of the volute and, therefore, the flow of exhaustgas into the turbine wheel One example of a variable volute design isU.S. Pat. No. 4,177,005 to Bozung. The design can be slow in respondingto sudden changes, is used solely as a braking application, and itsperformance can be negatively affected by debris build-up on the slidingwall surfaces. Another example is US 2011/0052374 to Arnold. This designmakes use of a flexible dividing wall that moves along a path to varythe discharge area into the turbine wheel. The design is complicated andfailure-prone because the chain and bearing mechanism used to move thewall are in the path of the hot exhaust flow.

Variable geometry turbochargers use adjustable guide vanes arrangedabout the turbine wheel in order to control exhaust gas flow to thewheel. These designs require a large number of expensive componentsalong with sophisticated software and controls.

Electrically driven turbines essentially turn the shaft of the turbinerotor into an armature. Because the armature must be disengaged once theturbine rotor spins up to a certain speed, these designs entailcomplicated electro-mechanical structures.

A moveable wall design for a variable geometry turbocharger is disclosedin US 2012/0036849A1 to Watson et al. (“the Watson publication”). Apivoting wall located along the upper wall of the housing pivots about apoint located upstream of the housing tongue and near the entry to thehousing (compare U.S. 2010/0266390 to Henderson et al. showing apivoting wall located far downstream of the tongue). As the wall pivotsaway from the upper wall, the wall reduces the volume of exhaust gasflowing into the volute. Alternatively, a rotating wedge segment can belocated along the upper wall of the housing and moved downstream toalter the cross section of the volute. However, neither the wall nor thewedge can prevent exhaust air from flowing into the turbine wheel evenwhen fully closed or deployed, nor can either one alter or extend theend of the housing tongue. Additionally, an equal amount of exhaustcannot flow over and under of the pivoting wall or wedge because thereis no neutral position.

A moveable or variable vane design, which is intended to minimize theoccurrence of turbo lag, is described in U.S. Pat. No. 7,481,056 toBlaylock et al., Turbocharger with Adjustable Throat, issued Jan. 27,2009 (“Blaylock”). A flow control gate is positioned in the center ofthe inlet to the housing on the exhaust side of the turbocharger andadapted, from a command, to momentarily rotate or pivot downstream abouta transverse hinge from a neutral first position to a second positiontoward the blades of the turbine rotor. (There is no open position abovethe neutral position.) In the second position, the control gate reducesthe volume of exhaust gas flowing along an inner flow path toward theturbine rotor and increases the air velocity and pressure upon theturbine rotor. This causes the turbocharger to reach optimal operatingspeed to substantially reduce or eliminate harmful emissions whileincreasing initial engine takeoff power and reducing lag time from whenspeedup was first signaled by the operator. Once the turbine is spun up,the control gate returns to a neutral position. When in the neutralposition, the operation of the turbocharger is as a standardturbocharger. The typical time for the gate action is a very small partof a second before returning to the neutral position. A properly sizedturbocharger could eliminate the need for a waste gate and theturbocharger could be large enough to handle the total exhaust flow atmaximum horsepower.

Still others have mechanically coupled the turbocharger to the engine.This type of arrangement, called “turbocompounding,’ is described in theSeptember 2010, North American edition of the trade magazine, DieselProgress (see “Could SuperTurbocharger Become the Hero on FuelEconomy?”). The turbocharger adds a small additional horsepower boostthrough the combination of the turbocharger and its transmission.However, turbocompounding entails complexity and involves additionalproduction cost all in hopes of achieving at most a 7% fuel savings ondiesel engines.

A flow control gate which momentarily alters the A/R (Area/Radius) ratioof a turbocharger in order to eliminate turbo lag is desirable (compareDE 31 05 179 A1 which discloses a gate that lies along the outer wall ofthe housing and outside the inlet or throat section and, therefore,cannot alter the A/R ratio of the housing). It is well known in the artthat the A/R ratio is the inlet cross sectional area dived by the radiusfrom the turbo centerline to the centroid of that area. The inlet (orthroat section) of a turbocharger extends between the end of the housingwhich mounts to the exhaust manifold and the tip or end of the tongue ofthe housing. To calculate the A/R ratio,

-   -   the area of the turbine housing is measured in square inches of        a cutting plane line that passes through the turbine's gas        passage at the tip of the tongue, divided by the radius from the        center of the turbine wheel's axis of rotation, to the centroid        of the volute. The tongue tip is the entry point of the turbine        housing where exhaust gas flow begins to reach the turbine wheel        inducer.

(see Jay K. Miller, Turbo: Real World High Performance TurbochargerSystems 45 (CarTech 2008)).

From the above, it is clear that:

-   -   1. The “A” in the A/R ratio is determined by the cross-sectional        area defined by a cutting plane line that passes through the        turbine's gas passage at the tip of the tongue to the opposing        wall of the inlet channel;    -   2. The inlet area A can be changed by making a new housing with        a different sized area A; and    -   3. The throat or inlet extends to the end of the tongue but not        beyond it.

The ability to alter the area of the inlet is important. For example,reducing the throat cross-section results in higher boost pressures.Turbocharger housings are designed with different A/R ratios along withcomplicated means (e.g., variable geometry turbines) to achieve thedesired performance. Other than Blaylock's flow control gate whichattempts to adjust the throat, the A/R ratio in prior art pivoting vanedesigns remains fixed because, absent making a new housing, there is noway for those designs to alter either the throat area or the radius fromthe center of the turbine wheel. However, Blaylock cannot alter wherethe tongue tip or tongue end of the housing begins and ends in real timeand, because of the location of the pivot point (at about the center ofthe vane), cannot close flow completely.

SUMMARY OF THE INVENTION

An improvement to a turbocharger having a housing with a slot locatedalong a midline of the housing and above the turbine wheel and a tonguedefining the end of an inlet throat area of the housing, the slotpermitting inlet exhaust gas which flows past the tongue to flow intothe turbine wheel, the improvement being a pivoting vane of fixed lengthaligned with the slot and located at a downstream end of the tongue.When the vane is in its fully closed position, the inlet exhaust gas isprevented from flowing into the slot and, therefore, the turbine wheel,until the inlet exhaust gas passes the end of the vane. The Preferably,the vane is arranged such that exhaust gas flow passing over thedownstream end of the vane is prevented from passing between the vaneand where it meets the downstream end of the tongue.

The A/R ratio of the housing progressively varies as the vane pivotsbetween the fully opened and fully closed positions. When the vane is inthe fully opened position, the initial (first) inlet throat area remainsunaltered and, therefore, so does the A/R ratio of the housing. When thevane is in the fully closed position, the inlet throat area changes to arevised (second) inlet throat area having a reduced cross-sectionalarea. The A/R ratio changes. When the vane is in the fully closedposition, the end of the vane extends to 180° of the slot. However, thelength of the vane can be any length that provides a desired A/R ratiowhen the vane is in the fully closed position yet still clear theturbine wheel when moving into the fully opened position, with shorterlengths being less effective than longer lengths.

The vane can further include a vertical divider wall located above andattached to the vane. When the vane is in the fully closed position, thevertical divider wall defines a first and a second volute of thehousing. A vertical divider wall may also be located in the inlet throatarea of the housing, upstream of an upstream end of the vane.

One preferred embodiment of a turbocharger with a variable A/R ratiomade according to this invention includes a moveable divider with avolute slot blocker or vane attached to it. In the open position, themoveable divider opens the housing to its original A/R ratio. As themoveable divider pivots towards the closed position, a volute slotblocker or vane connected to the bottom of the divider changes itsposition relative to the tongue tip or tongue end, thereby progressivelyvarying the A/R ratio. In the closed position, the upstream end of thevane meets the tongue end of the housing. A reduced A/R ratio results.Movement between the open and closed positions can be controlled viaelectrical or pneumatic control means.

In another preferred embodiment, the moveable divider is eliminated andthe volute slot blocker or vane, which lies at the downstream end of thetongue end, pivots between the open and closed position. The volute slotblocker can be controlled either electrically or pneumatically.

The objectives of this invention are to provide a turbocharger designthat (1) is simple in its design and control; (2) can be retrofitted toexisting turbocharger designs; (3) “spins up” the turbine wheel quickly;(4) progressively varies the A/R ratio; (5) does not create turbulencewhen varying the A/R ratio; (6) does not create backpressure in theinlet throat area; and (7) eliminates the need for a waste gate andother complicated structures intended to control back pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section of a preferred embodiment of a turbochargerwith progressively varying A/R ratio made according to this invention.The housing includes two dividers, one fixed, the other moveable. Thefixed divider (or flow splitter) is located entirely within the inlet orthroat section of the housing. The moveable (or pivoting) divider, whichis shown in its fully open position, begins at the end of the fixedthroat divider and then extends past the end of the tongue. The moveabledivider includes pivot means for allowing it to move between the fullyopen and fully closed position and includes a volute slot blocker orvane attached to its lower end (and outside of the original inlet orthroat section of the housing). A secondary housing (not shown) andcovers the divider and prevents exhaust gas from escaping theturbocharger housing.

FIG. 2 is a cross-section of the turbocharger of FIG. 1 with themoveable divider shown in the fully closed position. In the fully closedposition, the upstream end of the volute slot blocker or vane meets upwith the tongue end of the housing, thereby altering the A/R ratio byextending the tongue to the downstream end of the vane.

FIG. 3 is an end view of the throat or inlet section to the turbochargerfitted with the volute slot blocker or vane of FIG. 4. The pivot meansare located at the horizontal centerline of the inlet above the tongueend.

FIG. 4 is an isometric view of an alternate embodiment of the voluteslot blocker or vane. The moveable divider wall of FIG. 1 has beeneliminated along with the fixed divider.

FIG. 5 is a view of the vane of FIG. 4 in its closed position. The vanepreferably blocks the first 180° degrees of the volute slot. The vanecould extend past 180° but anything more than 185° would requireadditional means to pivot the vane away when moving toward the openposition and still clear the turbine wheel housing.

FIG. 6 is a top view of the vane of FIG. 4 with a portion of the housingcut away to show the vane.

FIG. 7 is a cross section of another preferred embodiment of aturbocharger with progressively varying A/R ratio made according to thisinvention. A volute slot blocker, shown in its open position here andarranged at the downstream end of the tongue, pivots downward toward theturbine wheel and effectively moves the end of the tongue (and,therefore, the inlet or throat section) further downstream to a place ofreduced cross sectional area, thereby resulting in a reduced A/R ratio.

FIG. 8 is a cross section of the turbocharger of FIG. 6, with the voluteslot blocker in its fully closed position.

FIG. 9 is an end view of the throat or inlet section to the turbochargertaken along section line 9-9 of FIG. 8. The pivot means are located atthe downstream end of the tongue, thereby not obstructing the originalthroat or inlet section area (compare FIG. 3).

FIG. 10 is a graph comparing the boost gain of a turbocharger fittedwith the embodiment of FIGS. 6-8. with and without the volute slotblocker.

FIG. 11 is a graph comparing a dynamometer run of the same turbochargerwith and without the volute slot blocker of FIGS. 6-8. The turbochargerwith the volute slot blocker makes more power and achieves peak powerabout 2 seconds faster.

FIG. 12A is an animation illustrating exhaust air flow as it flows fromthe exhaust air inlet to the wheel with the vane closed and the pivotpoint of the vane not obstructing the initial inlet throat area.

FIG. 12B is an animation illustrating the exhaust air flow when thepivot point of the vane is arranged at the centerline of the initialthroat area.

FIG. 13A is an animation illustrating the vane arrangement of FIG. 12Awhen the vane is opened at about 40° (as measured from the 180° point ofthe volute slot).

FIG. 13B is an animation illustrating the vane arrangement of FIG. 12Bwhen the vane is opened at about 25°.

ELEMENT NUMBER AND ELEMENTS USED IN THE DRAWINGS

-   10 Housing-   11 Inlet passageway or throat section-   12 Extended inlet passageway or throat section-   13 Volute-   15 Tongue-   17 Tongue tip or end-   19 Exhaust gas inlet side-   21 Cross section of 11-   23 Reduced cross section downstream of 11-   25 Volute slot above turbine inducer or wheel-   27 Wall-   29 Turbine inducer or wheel area-   30 Fixed divider or vertical wall (flow splitter)-   31 Downstream end of 30-   40 Moveable divider or vertical wall-   41 Pivot shaft-   45 Upstream end of 40-   47 Lower end of 40-   50 Volute slot blocker or vane-   53 Pivot arm-   55 Upstream end of 50-   57 Downstream end of 50-   60 Fully closed position-   65 Neutral position-   70 Fully opened position

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, and first to FIGS. 1 and 2, a preferredembodiment of a turbocharger with an adjustable or progressivelyvariable A/R ratio made according to this invention includes a housing10 having two vertical walls or dividers of fixed length, onenon-moveable or fixed 30, the other moveable 40. The fixed divider orflow splitter 30 is located entirely within the inlet or throat section11 of the housing 10 and preferably has an arcuate (concave-shaped)downstream end 31 or, alternatively, a straight end (not shown). Themoveable (or pivoting) divider 40, which is shown in its fully openedposition in FIG. 1, begins at the downstream end 31 of the fixed divider30 and then extends past the end 17 of the tongue 15.

Housing 10 is a radial inflow housing, meaning that the housing 10 has avolute 13 that continuously decreases in area and cross section to helpmaintain even pressure all the way around the turbine inducer or wheelarea 29. The inlet or throat section 11 of the housing 10 begins at theexhaust inlet side 19 and extends to the end 17 of the tongue 15. Thisinvention effectively extends that original throat section 11 furtherdownstream in the volute 13 to an area of reduced cross section 23relative to that of the original or unaltered throat cross section 21(see FIG. 7 showing cross section 21 being defined by a cutting planeline that passes through the inlet passageway or throat section 11 atthe tip or end 17 of the tongue 15 to the opposing wall 27 of the inletpassageway 11 and cross section 23 being farther downstream defining anextended throat section 12).

The moveable divider 40 includes pivot means for allowing it to movebetween the fully open and fully closed positions 70, 60 (see e.g. FIG.7). The pivot means is preferably a shaft 41 in communication withelectrical or pneumatic control means of a kind known in the art (seee.g., U.S. Pat. No. 7,481,056 to Blaylock, the contents of which ishereby incorporated by reference). The control means is sized towithstand and overcome any backpressure exerted by the divider 40 andvane volute slot blocker or vane 50 (discussed below) when movingbetween the closed and open positions 60, 70.

The shaft 41 is not in contact with the upper wall 27 of the housing 10but rather is arranged at the horizontal center line of the throatsection 11. The upstream end 45 of the divider 40 preferably has anarcuate (convex) forward end or straight end complementary in shape tothe fixed splitter's downstream end 31.

The moveable divider 40 also includes a rigid (non-flexible), voluteslot blocker or vane 50 attached to the lower end 47 of the divider 40.The upstream end 55 of the vane 50 begins at the end 17 of the tongue15.

When the moveable divider 40 is in the fully open position, the A/Rratio of the housing 10 remains unchanged. The divider 40 opens up thevolute 13 and provides a single volute design to the housing 10, withexhaust gas flow flowing between the end 17 of the tongue 15 and theupstream end 55 of the vane 50 (and therefore under and over the vane50) until it eventually flows into the turbine inducer or wheel area 29.

When the moveable divider 40 is in the fully closed position, theupstream end 55 of the volute slot blocker or vane 50 meets up with theend 17 of the tongue 15, and the moveable divider 40 provides a dualvolute 13 housing 10. The A/R ratio is altered because the tongue end 17(and therefore the inlet passageway or throat section 11) has beenextended by the vane 50 toward the downstream end 57 of the vane 50.

This extension effectively brings the tongue end 17 to a place ofreduced cross sectional area 23 relative to the original inlet or throatcross sectional area 21, thereby resulting in a reduced A/R ratio. Forexample, when in the closed position, the vane 50 turns a 0.88 A/Rturbine housing (i.e., a housing with the vane 50 in a fully retractedposition or a housing without the vane 50) into a 0.40 A/R turbinehousing.

As the moveable divider 40 and volute slot blocker or vane 50 move tointermediate positions (e.g. 65) between the fully opened and fullyclosed positions 60, 70, the A/R ratio is progressively varied. Usingthe above example, the A/R ratio can progressively vary between 0.88 and0.40. However, the length of the vane 50 can be any length that providesa desired A/R ratio when the vane 50 is in the fully closed position 60yet still clear the turbine inducer or wheel area 29 when moving intothe fully opened position 70, with shorter lengths being less effectivethan longer lengths.

When the movable divider 40 is in its fully open position, the divider40 extends beyond the original housing 10. A secondary housing (notshown) is needed to cover the divider 30 and prevent exhaust gas fromescaping the housing 10.

Referring now to FIGS. 3-6, an alternate preferred embodiment of aturbocharger with an adjustable or progressively variable A/R ratio madeaccording to this invention includes a housing 10 having the volute slotblocker or vane 50 of fixed length without the fixed and moveabledividers 20, 40 of FIGS. 1-3. Similar to that other embodiment, vane 50preferably blocks the first 180° degrees of the volute slot 25 when thevane 50 is in the fully closed position (see e.g., FIG. 5). The pivotshaft 41 is located at the horizontal centerline of the inlet or throatsection 11 above the downstream end 17 of the tongue 15.

Preferably, the vane 50 is arranged such that exhaust gas flow passingover the downstream end 57 of the vane 50 is prevented from passingbetween the vane 50 and where it meets the downstream or tip end 17 ofthe tongue 15 (see e.g., FIGS. 12A-13B).

Animations show that leaving the inlet 11 unobstructed by the shaft 41(and arm 53) produces a much smoother flow of exhaust gas in the volute13, through the slot 25 and into the turbine inducer or wheel area 29(see FIGS. 12A-13B, the arrows showing the flow, the line weight of thearrows indicating velocity, with the line weight increasing as velocityincreases; note the flow exits the turbine wheel but is notillustrated). Also, placing shaft 41 in the center of the inlet createsbackpressure, even if knifing means (not shown) are placed upstream ofit. Ideally, the backpressure-to-boost ratio is about 1:1.

Therefore, in the embodiment of FIGS. 7-9, the pivot shaft 41 is locatedbelow the inlet cross sectional area 21 so that the shaft 41 does notobstruct the inlet cross sectional area 21 at any time. The pivot pointor shaft 41 does not contact the upper wall 27. Preferably, only asingle pivot shaft 41 is used in this and the other embodiment. Alsopreferably the vane 50 is arranged such that exhaust gas flow passingover the downstream end 57 of the vane 50 is prevented from passingbetween the vane 50 and where it meets the downstream or tip end 17 ofthe tongue 15 (see e.g., FIGS. 12A-13B).

Additionally, the angled pivot arm 53 in the embodiment of FIGS. 3-6 hasbeen eliminated. The upstream end 55 of the vane 50 is attached at theend 17 of the tongue, which permits the vane to close the first 180° ofthe slot 25 completely (and also makes the vane stronger compared to adesign which places the pivot point at a min-point of the vane).Preferably, the upstream end 55 is set lower or deeper relative to thevolute slot 25 than is the downstream end 57 of the vane 50. In apreferred embodiment, the upstream end 55 was set about ⅛ inch (0.317cm) lower than the downstream end 57.

Vane 50 can be sized such that it can be received by the volute slot 25yet still block flow into the slot 25 (e.g., ½ inch (1.27 cm)) or can besized wider than the slot 25. Making vane 50 wider than slot 25 servesto raise the vane 50 higher in the volute 13, thereby decreasing thecross-sectional area above the vane 50. The same holds true for theother preferred embodiments

The fully open position 70 is above the full intermediate or neutralposition 65 which, in turn, is above the fully closed position 60 (seeFIGS. 7 & 8). The neutral position 65 essentially splits or definesvolute 13 into an upper and lower half, with an equal volume of exhaustflowing over and under the vane 50. The vane 50 can pivot from any oneof those positions 60 65, 70 to another as well as any position inbetween each of those. As the volute slot blocker or vane 50 pivotsdownward from the open position 70 toward the turbine inducer or wheelareaa 29, the vane 50 effectively moves the tongue end 17 (and,therefore, the inlet or throat section 11) further downstream to a placeof reduced cross sectional area 23, thereby resulting in a reduced A/Rratio. When in any position other than the fully open position 70, theA/R ratio of the turbocharger is altered.

When vane 50 is in the closed position, tests showed a 3,000 RPMincrease in turbine wheel speed at idle. By way of comparison, theBlaylock moveable vane, discussed in the Background section, shows a 500RPM increase at idle. A reason for this is the Blaylock moveable vanecannot close off flow to the turbine wheel completely. Vane 50 can closeoff the flow to 180° of the slot 25. Similar to the other preferredembodiments, the length of the vane 50 can be any length that provides adesired A/R ratio when the vane 50 is in the fully closed position 60yet still clear the turbine wheel when moving into the fully openedposition 70, with shorter lengths being less effective than longerlengths.

FIG. 10 shows the boost gain of a turbocharger without a volute slotblocker and the same turbocharger fitted with the embodiment of FIGS.4-8. FIG. 11 compares a dynamometer run of the same turbocharger withand without the volute slot blocker 50. The turbocharger with the voluteslot blocker 50 makes more power and achieves peak power about 2 secondsfaster.

While preferred embodiments of the turbocharger have been described, theinvention itself is defined by the following claims.

What is claimed:
 1. An improvement to a turbocharger having a housing(10) defining a slot (25) located along a midline of the housing (10)above a turbine wheel (29) and a tongue (15) defining the end of aninitial inlet throat area (11) of the housing (10), the slot (25)permitting inlet exhaust gas which flows into the initial inlet throatarea (11) and past the tongue (15) to flow into the turbine wheel (29),the improvement comprising: a vane (50) co-aligned with the slot (25)and having an upstream end (55) located at a downstream end (17) of thetongue (15); means for pivoting (41) the vane (50) between a fullyclosed (60), a neutral (65), and a fully opened position (70), the pivotmeans (41) arranged at the downstream end (17) of the tongue (15) andthe upstream end (55) of the vane (50); wherein when the vane (50) is inthe fully closed position (60), the inlet exhaust gas is prevented fromflowing into the slot (25) until the inlet exhaust gas passes adownstream end (57) of the vane (50).
 2. An improvement according toclaim 1 wherein the A/R ratio of the housing (10) progressively variesas the vane (50) pivots between the fully opened (70) and fully closedpositions (60).
 3. An improvement according to claim 1 wherein in thefully opened position (70) the flow of the inlet exhaust gas is unevenlydistributed above and below the vane (50).
 4. An improvement accordingto claim 1 wherein the overall length of the vane 50 is sized to providea predetermined A/R ratio when the vane (50) is in the fully closedposition (60) yet still clear the turbine wheel (29) when moving intothe fully opened position (70).
 5. An improvement according to claim 4wherein when the vane (50) is in the fully closed position (70) thedownstream end (57) of the vane (50) extends to 180° of the slot (25).6. An improvement according to claim 1 wherein the vane (50) is widerthan the slot (25).
 7. An improvement according to claim 1 wherein theupstream end (55) of the vane (50) is at a different height relative tothe slot (25) than is the downstream end (57) of the vane (50).
 8. Animprovement according to claim 1 further comprising a vertical dividerwall (40) located above and attached to the vane (50).
 9. An improvementaccording to claim 8 wherein when the vane (50) is in the fully closedposition (60), the vertical divider wall (40) defines a first and asecond volute (13) of the housing (10).
 10. An improvement according toclaim 1 further comprising a vertical divider wall (40) located in theinlet throat area (11) of the housing (10), upstream of an upstream end(55) of the vane (50).
 11. An improvement according to claim 1 whereinthe pivot means (41) does not obstruct the flow of inlet exhaust gasflowing through the inlet throat area (11) of the housing (10).
 12. Animprovement according to claim 1 wherein the vane (50) is a fixedlength.
 13. An improvement according to claim 1 wherein the vane (50) isa rigid vane.
 14. An improvement according to claim 1 wherein inletexhaust gas passing a downstream end (57) of the vane (50) cannot passbetween the vane (50) and the downstream end (17) of the tongue (15).